1. Field of the Invention
The invention relates to a pressing device for pressing of shaped compacts, especially from a pulverized material.
2. Description of the Related Art
Generally, presses of that kind serve for pressing of powder or granulates made from iron, plastic material, hard metal, ceramic base materials or the like, to compacts, e. g. gears or molded parts. Because of the high specific compression pressure of partly 30–100 kN/cm2 and more, a very high stability of the pressing device is required.
Schaidl et al., U.S. Pat. No. 4,482,307 (DE 31 42 126 C2) discloses a modular press comprising the actual press for applying a main pressing force and a pressing device, which, adapter-like, can be inserted in the actual press. This insertable pressing device comprises a tool frame, which via an upper and a lower connection device is coupled between the two press rams of the press. Basically, the adapter-like pressing device consists of a frame structure of pull rods for guiding a plurality of plates, punch carriers and a die plate located between the connection devices which are also arranged or mounted on a bearing on said frame structure. According to this arrangement a base plate having hydraulic devices for the relative moving of single plates, which are configured as punch carriers, is supported in the actual press with a bearing attachment. In relation to this base plate, the further plates are supported in the frame structure in a displaceable way. Via the frame structure, the die holding plate is rigidly connected with the lower connecting device of the adapter and with regard to the upper connecting device of the adapter arranged in the frame structure in a movable way. In relation to the base plate, the individual punch carriers are hydraulically movable, being therefore, as a result of it, displaceable between a filling position, in which the die opening of the die holding plate can be fed with powder, and a final press position, in which the powder is pressed into a compact by press punches. The punches for pressing the powder are seated on the respective punch carriers. When being in the final press position the respective punch carriers are supported on end stops. Both, piston/cylinder devices for the hydraulic driving of the individual punch carriers as well as the end stops, especially fixed stops, are arranged in the outer peripheral region of the punch carriers and being spaced away from the respective central openings of the individual punch carriers. There, the central openings in the individual punch carriers are configured in such a way, that always those punches, which are seated on a punch carrier, which is more distant from the die holding plate, can be guided through the openings of those punch plates which are situated nearer to the die holding plate.
To improve guidance of the punch carriers there is known from Fleissner et al., EP 436,792 (DE 40 00 423 C2) a press for producing shaped compacts from powdered material, which comprises an upper and a lower press ram and a tool frame being adapter-like inserted in the press and being via a lower coupling plate connectable with the lower ram and being connectable via an upper connecting piece with the upper ram. On a base plate of the tool frame, which is firmly supported in the press, there is provided a displaceably supported frame structure of pull rods, which rigidly connect the lower coupling plate with a die holding plate. Furthermore, punch carriers are movable from the base plate into the filling and press position by piston/cylinder drives. For improvement of the guidance it is suggested the punch carriers to be designed as pots being guided relative to the base plate along cylindrical surfaces. Also in this arrangement the punch carriers are supported against end stops in the final press position.
Both arrangements require a careful adjustment of the individual punch carriers relative to each other and relative to the frame structure, in order to avoid wedging or uneven pressing. A particular problem in this process is the position of the end stops, which from the base plate touch the lower part of the outer rim of especially the third punch carrier far distant from the central opening. In the final press position as a result of it, the corresponding punch carriers are supported on an end stop on its outside while an opposite pressing force is acting on the punches, which in the neighboring through opening are supported on the inner side. This causes a deflection of the punch carrier, which in practice has to be compensated with a plurality of single trials in order to adjust the pressing forces. Furthermore, for high press cycles, re-adjustment has to be carried out, regularly, in order to compensate, for example, influences of fluctuating powder qualities.
Furthermore, such presses for manufacturing of shaped compacts are disclosed in DE 42 27 640 A1 or U.S. Pat. No. 4,392,800.
In Rau et al., U.S. 20030015813 A1 (DE 101 35 523) a pressing device is disclosed, in which supporting devices are arranged for supporting of punch carriers between a base body and the relating punch carriers such that punches sitting on the punch carriers are centrally supported in the final press position via the supporting devices acting in the line of force.
An object of the invention is to improve a press for the manufacturing of shaped compacts, essentially from pulverized material in such a way that a frame structure having different components to be inserted in a press can be easily assembled for the most different requirements. A further object of the invention with respect to the supporting devices is to provide an improved arrangement for the punch carriers.